Liquid damped telescopic shock absorber



June 26, 1945. P. w. THORNHILL LIQUID DAMPED TELESCOPIC SHOCK ABSORBER Filed Jan; 11, 194s 1 m n A Patentedlunez, 1945 2.31am i uovm om nuscorrc snocx moana Peter Warhol-l Si., lll- Thornhlllieamingten land,asaignortoJahn llenrynienacoveliry,

Applieationlanaary l1, 1943, Serial No. 472,042 In Great Britain January 23, 1942 This invention relates to liquid damped telescopic shock absorbers. and it has for its object to provide constructional improvements which are useiul in cases where it is desired that the plunger member or equivalent of the telescopic shock absorber shall be adapted to have a substantial amount of freedom to move in a lateral direction relative to the usual cylinder. 'Ihe invention is oi particular utility where the usual cylinder is iix'ed and the plunger member or equivalent is connected pivotally to a member which moves anguiarly so that the point of attachment of the v plunger member or equivalent to said member travels along an arcuate path.

It is a further object of the invention to provide an exceptionally simple form and construction oi oleo-pneumatic shock absorber which is particularly suitable for use in tbe landing gear of aircraft. It will, however, be understood that the improved shock absorber may be used as a suspension unit for road and other vehicles.

In a liquid damped telescopic shock absorber in which a tubular plunger member having a piston at its inner end rocks relative to a cylinder as the piston slides within said cylinder, the present invention is characterized by the fact that a recoil damping piston, connected to the cylinder by a longitudinal stem extending into the plunger member, is slidable within the plunger member, andmeansareprovidedtoenabletherecoil damping piston to accommodate itself to variable eccentricity of the plunger member.

There is further provided according to the invention a liquid damped telescopic shock absorber comprising in combination a cylinder closed at one end, a tubular plunger member extending into the cylinder and having a piston head at its inner end. the other end of the plunger member being closed, a stem secured to the closed end of the cylinder and extending through the piston head into the plunger member, a recoil dampinl piston carried by the end oi` said stem, and means for enabling the recoil piston to occupy an eccentric position with respect to the bore or the cylinder.

As another aspect o! the invention, a liquid damped telescopic shock absorber is provided comprising in combination a cylinder closed at one end, a tubular plunger member extending into the cylinder and having a piston head at its inner end, the other end of the plunger member being closed,astemextendingfromtheclosedendor the cylinder through the piston head and into the plunger member, a recoil damliinl piltn disposed within the plunger member and carried by occupy an eccentric position with respect to the bore ot the cylinder, a iioating piston slidabie within the plunger member between the recoil dampins piston and the closed outer end of the plunger member. and a damping valve device arranged in restrict the ilow of damping liquid from the plunger member to the cylinder.

'Ihe recoil damping piston can conveniently comprise an annular disc which is disposed within a groove formed in the stem or in a member carried thereby, said disc being located against axial movement but being free to move radially to accommodate itself to rocking movements of the plimger member, while in an alternative arrangement the recoil damping piston comprises an annular disc which engag a head formed upon the stem and is radially slidable relative to said stem so as to permit the plunger member to rock within the cylinder. In a still further modification the .recoildampingpistonisslidablymountedinthe plunger member and is connected with the stem by means of a pivotal joint, conveniently of the universal type.

. The invention is illustrated by way of example es in the accompanying diagrammatic drawing, in

which- Figure 1 is a sectional side elevation of one form o! shock absorber Figure 2 is a fragmentary sectional elevation ao showing a modiiied construction oi' stem and recoil damping piston;

Figure 3isaviewsimilarto1l'igure 2 but showing a still further modification; and

Figure 4 is a view in elevation similar to Figure l but disclosing a castoring mounting wherein the plunger is rotatable relative to the cylinder.

The shock absorbing device shown in Figure i comprises a tubular cylinder i0, the top of which is closed by an upper wall Ii having an integral lug Il by which the shock absorbing device is attached to the aircraft or equivalent, usually in a rigid manner, a second iixing joint being provided by a hole il formed in a depending lug I4, which latter is secured to a sleeve I5 fastened to the lower part o! the cylinder Il. A lever I6 is pivoted at i1 to the lug I4 and carries a wheel or like landing member (not shown) at its free end.

'I'he lever i0 is formed intermediate its length 50 with a lug il to which is pivotally attached at i! a phmger member 2l which extends upwardly within the cylinder Il and is also tubular in form. The plimger member 2l is smaller in diameterthanthecylinder ilsoastobeable thestem,meansior enablingtherecoilpistonto ss to rockirom side to side and thus compensate forthscurvedpathtakenbythepivotilasthe (relativetothecylinderilandtherecoildampieverilmovesupanddown 'lheuppsrendot ingpistonillllsothattheairdisposedinthe thepiungermemberiliahoweveniittedwitha spacellhasitspressureraisedquiteconsiderwall il ofthecylinder Il and palesthrough an apertureinthepistonheadlLsaidapertiu'e beingenlargedatitsupperandlowerpartaasindicated.soastopermittherockingmovementof the piston head Il. The lower end of the stem 21 is formed with a head Il, which latter is grooved circumferentially at Il for the accommodation of anannulardisclhtheholeinthediscbeinglarserindiameter than the bottom of the groove II soastoenablesaiddisctoslideradiallyrelativeto the stem Il as the plunger member Il rocks from side toside. The outer periphery of the disc Il is arranged to slide snugly within the plunger member 2l andsaid disc Il, inconiunction withthe head 20, constitutes a recoil damping piston separatingaliquidspacellbelowthepistcn from a liquid space Il disposed between said recoil damping piston Il. 3| and the piston head 2i: the liquid spaces 32 and Il, are however, in communication with one anotherthrough a constrlcted by-pass passage Il. The piston head 2| is formed with a plurality of liquid passages Il which are controlled by an annular damping valve member Il having its downward opening movement limited by a stop flange l1; one or more constricted passages Il are formed in the damping valve member It so that even when the latter is in its raised position liquid is able to flow at a very limited rate into the cylinder space', which is indicated at 3l and which is full of liquid. It will, loi' course, be understood that in the axial shock absorbing device a plug or equivalent fitting (not shown) would be provided in the cylinder Il for the insertion of the damping liquid and an air inlet valve (not shown) would similarly be fitted to the lower part of the plunger member 2l to enable compressed air to be pumped in until the requisite internal pressure is obtained for supporting the normal load to be carried by the device. Downward movement of the plunger member 2l is limited by a stopwhich is indicated diagrammatically at 4I, while in order to protect the working parts from dirt and other foreign matter the lower part of the plunger member 2l slides snugly through an annular disc Il, which latter is located in a housing I2 arranged tc permit said disc to have a requisite sliding movement in a radial direction, thus enabling the plunger member 2l to rock within the cylinder Il.

'lhe operation of the shock absorbing device shown in Figure 1 is as follows. When the wheel or equivalent encounters a bump the lever It rises. thus causing liquid to be expelled fairly readily through the passages Il, past the open damping valve Il and into the space Il. This space Il. although it is expanding. cannot hold all the liquid expelled from the cylinder space It and therefore some of the liquid flows through the by-pass passage Il into the space 32. This liquidpressesdownthefloatingpiston llandat thelametimetheplungcrmemberllisrising downward movement is limited by the which the liquid from the space I8 can escape through the constricted opening or openings il in the damping valve member Il, which latter, of course, assumes its upper closed position immediately the downward movement of the plunger member Il commences.

Ihe modified form of recoil damping piston showninlig'ure2isarrangedasavaiveperiorm-- ingthe functions oi the damping valve It in Hgure l. Porthispurpose theannulardiscti rests upon a plain ilange Ila constituting a head upon the stem 21. The latter is formed with an axial bore having a damping constriction u at its lower end, and communicating with the cylinder .space Il by way of-openings 4I. The annular disc gg openings Il, bore Il, and constriction Il to the liquid space l! below the recoil dampinl piston Ila; Il; during this movement, of course, the space 88 becomes enlarged and liquid is readily able to ilow thereinto from the space Il by lift- 0 ing the disc 3l away from the head Ila. When recoil occurs, however, the liquid is trapped within the space Il and can only escape at a relatively slow rate by flowing through the constriction or constrictions Ila into the cylinder space ll, thus positively retarding the downward movement of the plunger member 2l relative to the cylinder Il.

The arrangement shown in Figure 3 functions inthesamemannerasthat showninFigure l but includes an alternative mechanical arrangement of the recoil damping piston. This piston. which is indicated at IIb, is arranged to nt snugly within the plunger member Il and has its external grooved surface shaped part-spherical so that the piston member Nb is able to rock or tilt within the plunger member Il and at the same time maintain a reasonable liquid tight tit therein. Prom its upper surface projects a socket Il which, in conjunction with a ball member 4I, constitute! a universal Joint connecting the recoil damping piston 2lb with the stem 21. It will be noted that the centre ot the bali l0 is displaced axially to a considerable extent with respect to the general plane of the recoil damping piston 2lb and this. of course, is necessary tor it permits the plunger member 2l to rock within the cylinder il; it will be realised that as the plunger member 2l moves to one side the ball Il becomes eccentrically disposed with respect to the plunger member 2l and therefore the recoil damping piston lib tilts over to accommodate this ecoentricity. In calm where the rocking movement of the plunger msmber Il is confined to a Single plane the universal Joint Il, il may be substituted by a simple pivotal point having its axis at right angles to that 76 plane.

It will, of course, be understood that the constructions which have been described are given merely by way of example and that various modications may be made. For instance, it is conceivable that the device can be arranged to serve as a castoring mounting for a tail wheel or the like by fastening the cylinder I to the aircraft fuselage and arranging for the sleeve I to be rotatable upon said cylinder. 'I'his may be done as shown in Figure 4 by providing a collar or other abutment A to prevent vertical displacement of sleeve Il.

What I claim is:

1. In a liquid damped telescopic shock absorber including a cylinder, a tubular plunger and a piston on the inner end of said plunger, said piston fitting in said cylinder for rocking movement and defining therewith a primary working space; the combination which comprises a stem rigid with said cylinder and extending through said piston into said tubular plunger. and a member which is slidable within the tubular plunger and is carried by the stem with freedom to move laterally relative to said stem as the plunger rocks 4within the cylinder, said slidable member defining with said tubular plunger and said piston a secondary working space. for establishing free communication between said primary and second working spaces under compression and restricted communication therebetween under extension.

2. In a shock absorber as claimed in claim 1. a oating piston subdividing the tubular plunger between its outer end and said slidable member into two zones. the zone most remote from said means having air therein.

3. In a shock absorber as claimed in claim 1, a head upon the lower end of the stem and a coiled compression spring urging the slidable member into engagement with the upper surface of said head. the slidable member .being in the form of an annular plate having its outer edge slidable snugly within the plunger tube. while its inner edge is a loose tit on the stem to permit said slidable member to move laterally relative to the stem as the plunger rocks.

4. In a liquid damped telescopic shock absorber including a cylinder, a tubular plunger and a piston on the inner end of said plunger, said piston fitting in said cylinder for rocking movement and denning therewith a primary working space; the combination which comprises a stem rigid with said cylinder and extending through said piston into said tubular plunger, a damping piston mounted on the end of said stem with freedom to move laterally relative to the stem as the plunger rocks within the cylinder. said damping piston deiining with said piston and said tubular plunger a secondary working space. and a check valve for establishingfree communication between said primary and secondary working spaces under compression and restricted communication therebetween under extension.

5. In a shock absorber as claimed in claim 4. in which the piston is provided with a plurality 'of apertures connecting the primary and secondary working spaces. said check valve comprising an annular member o! van external diameter substantlally equal to the internal diameter oi' the plunger and of an internal diameter greater than thediameterofthestemandhavingthereinrestricted orifices for registry with the apertures in the piston, and means limiting the axial movement of said annular member in said tubular plunger.

6. In a liquid damped telescopic shock absorber including a cylinder, a tubular plunger and a piston on the inner end of said plunger, said piston iitting in said cylinder for rocking movement and defining therewith a primary working space; the combination which comprises a stem rigid with said cylinder and extending through said piston into said tubular plunger. said stem having an annular slot therein adjacent its inner end, said slot being in a plane normal to the long axis of said cylinder. an annular washer in said slot having an internal diameter greater than the diameter of that portion of the stem defining the bottom of the slot. said washer deiining a secondary working space, and a check valve for establishing free communication between said primary and secondary working spaces under compression and restricted communication therebetween under extension.

7. In a liquid damped telescopic shock absorber including a cylinder, a tubular plunger and a piston on the innerend of said plunger. said piston iitting in said cylinder for rocking movement and defining therewith a primary working space: the combination which comprises a stem rigid with said cylinder and extending through said piston into said tubular plunger. a ball on the end of said stem, a damping piston, said damping piston having a socket cooperating with said ball so that said piston is capable of limited universal movement, said damping piston defining with said piston and said tubular plunger a secondary working space, and a check valve for establishing free communication between said primary and secondary working spaces under compression and restricted communication therebetween under extension.

8. In a shock absorber as claimed in claim '7 in which the periphery of said damping piston is partly spherical.

9. In a liquid damped telescopic shock absorber including a cylinder. a tubular plunger and a piston on the inner end of said plunger. said piston fitting in said cylinder for rocking movement and denning therewith a primary working space; the combination which comprises a stem rigid with said cylinder and extending through said piston into said tubular plunger. a radially extending iiange on the inner end of said stem. an annular member surrounding said stem and resting on said flange, said annular member having an external diameter approximately equal to the internal diameter o! the tubular plunger and an internal diameter greater than the external diameter of the stem. resilient means normally biasing said annular member against said flange. said annular member dividing said tubular plunger into upper and lower secondary working spaces, said primary working space being in communication with said lower secondary working thoieof.

PITIR WARBORN 'I'HORNHIIL 

